Modern war games and military training exercises use simulated weapons fire instead of live fire due to the high cost of munitions and restrictions on live weapons. The weapons that are simulated may range from small arms carried by soldiers and combat personnel to large caliber artillery mounted on tanks and armored vehicles. In a typical engagement simulation system, an infrared laser beam is fired from a laser transmitter mounted on a weapon to simulate firing of the weapon towards a target. A laser receiver at the target detects the laser beam and automatically determines its effect, including any hits, misses, damage, and so forth. The laser typically produces a number of short duration pulses that encode information about the nature of the weapon being simulated.
FIG. 1A illustrates a military training exercise involving an example of an existing laser engagement system 100 commonly referred to as MILES (multiple integrated laser engagement system). In a typical engagement, a first combatant 102 acquires targeting information on a second combatant 104 by aiming a cannon or other weapon at the second combatant 104. The first combatant 102 then activates a co-collimated laser transmitter 106 to simulate direct fire at the second combatant 104. The laser transmitter 106 emits a coded burst of laser pulses 108 towards the second combatant 104 that encodes within its pattern of pulses the nature and capability of the weapon being simulated by the first combatant 102.
At the second combatant 104, a receiver 112 receives and analyzes the laser pulses 108 from the transmitter 106 to determine, among other things, a range or distance from the first combatant 102 in order to estimate the degree of damage or lethality. The receiver 112 may also estimate marksmanship from the laser pulse 108, which is a measure of how well the second combatant 104 was hit. The range and marksmanship estimates are then provided to a control system (not expressly shown) of the second combatant 104 to use to determine the damage suffered by the second combatant 104. These range and marksmanship estimates may also be transmitted to a command center (omitted here) for storage and subsequent analysis in some cases.
Although not expressly shown, the first combatant 102 may also have a receiver, and the second combatant 104 may also have a transmitter. In fact, the transmitter and the receiver are commonly co-located and may also be implemented as a single integrated unit.
As can be seen, it is important that the receiver 112 be able to determine range and marksmanship for the second combatant 104 as precisely as possible. Incorrect range estimates may cause a hit to be declared on the second combatant 104 even though he/she/it may have been too far away based on the capabilities of the particular weapon being fired. Conversely, a hit may be declared to be inconsequential based on an incorrect estimate when in actuality the opposite is true. Similarly, inaccurate marksmanship estimates may cause a hit to be declared on the wrong combatant where multiple combatants are in close proximity to one another. Moreover, even if a hit turned out to be correctly declared, the amount of damage caused by the hit may still be incorrectly assessed (e.g., fatal versus only slightly damaged) if the range and/or marksmanship estimates are too far off.
For most laser receivers, the range may be estimated from the signal strength of the received laser pulses. Generally, short range weapon system simulators emit low laser power, medium range systems emit medium power and long range systems, such as battle tank main guns, emit high laser power to simulate lethal engagements at longer ranges. Unfortunately, this emitted power technique has a number of drawbacks in direct fire, line-of-sight systems like MILES. For example, dust, debris, smoke, rain, snow, and other atmospheric obstructions may block or otherwise obscure the path of the laser pulses, resulting in the reception of a weak signal by the receiver, while well within lethal range, that results in a hit being scored as inconsequential when it should be scored as lethal. Increasing the laser power to penetrate the obscured atmosphere is not an option because at the laser wavelengths used, higher power results in a potential for optically damaging the retina of persons who view the beam directly or aided by binoculars or other optical sighting systems. In addition, scattering of the laser beam by dust and other particles in the atmosphere or from the exit aperture of the laser transmitter can cause combatants that are not being aimed at to receive sufficient laser light that they mistakenly declare a lethal hit. As a result, one simulated shot may “kill” multiple targets incorrectly. In other words, scattering has the effect of spreading the laser beam out such that the laser beam profile, which is the area impinged by the laser beam when viewed on a perpendicular plane (as shown in FIG. 1B), appears to diverge and become larger than it would otherwise be in clear air. The enlarged laser beam profile caused by scattering effectively expands the “zone of lethality,” which is a smaller area 110 within the laser beam profile where the laser signal strength is deemed sufficiently strong to cause damage on a target. Such an expanded zone of lethality may have an adverse effect on the accuracy of the marksmanship determination.
The above drawbacks may become exacerbated in clustered environments where other combatants 114, 116, and 118 are in close proximity to the first and second combatants 102 and 104, as shown in FIG. 1. In such clustered environments, ambiguity often arises as to which combatant is shooting and which combatant is being shot. For the above reasons as well as other drawbacks, operational testing of new or experimental weapon systems are generally prohibited from being conducted with laser engagement systems such as MILES.
One effort to overcome the line-of-sight limitations associated with direct fire systems like MILES is to use GPS (global positioning system) to track the geo-positions of the combatants and to exchange messages by radio through a central control when simulating fire or determining engagement lethality. An example of a GPS-based geo-positioning system is OneTESS (One Tactical Engagement Simulation System) currently being developed by AT&T Government Solutions. However, while OneTESS and similar GPS-based geo-positioning systems bring the advantages of indirect fire simulation and may be able to effectively pair combatants in simple one-to-one and/or long range engagements, these systems presently lack adequate precision and bandwidth to unambiguously pair combatants where a large number of combatants are in a close range, clustered environment.
Accordingly, what is needed is a laser engagement system, and method therefor, that overcomes the deficits and shortcoming of existing and projected solutions to add unambiguous direct fire pairing to systems such as OneTESS and to potentially couple the solution with a laser wavelength choice that is not transmitted and focused on the retina by the human eye, providing greatly enhanced safety while allowing the laser transmitter to operate at high enough power to penetrate murky atmospheres.